Safety system for small x-ray units



Sept. 11, 1934. A.'MUTSCHELLER 1,973,415

SAFETY SYSTEM FOR SMALL X-RAY UNITS Tasuaa I1.

Filed July 1, 1929 3 Sheets-Sheet l Z 26 lEL'LRE E3 I I NVENTOR Ari/7m" fiutniwlier ATTORNEY Sept. 11, 1934. I A. MUTSCHELLER 1,973,415

SAFETY SYSTEM FOR SMALL X-RAY UNITS Filed July 1, 1929 3 Sheets-Sheet 2 *"LLEURE :5

9 I22 Arman/jaw fier MMMH ATTORNEY P 1934- A. MUTSCHELLER 1,973,415

SAFETY SYSTEM FOR SMALL X-RAY UNITS Filed July 1, 1929 3 Sheets-Sheet 5 ATTORNEY Patented Sept. 11, 1934 Umrso s'rAr s PATENT DFFICE SAFETY SYSTEM FOR SMALL X-RAY UNITS Application Julyl, 1929, Serial No. 375,036 4 Claims. (01. 250-34) My invention relates to safety. systems for small X-ray units, of a type suitable for use in dentistry and other special work of various kind requiring X-ray apparatus of extreme compactness and portability, combined with a reasonably high power. The purpose of my invention is to so construct and arrange an X-ray unit of the type just mentioned as to promote safety,.not only to the patient but also to the operator and to the apparatus.

My invention further comprehends the production of an X-ray unit of the generalcharacter here under discussion, and in which the X-ray tube and parts most immediately associated therewith are rendered relatively accessible, and are not submerged in oil or in any insulatorof a jelly-like consistency.

My invention further comprehends an X-ray unit in which as far as practicable all high tension leads and other high. tension connections are housed within the casing of the apparatus and in very close proximity to the X-ray tube; thus promoting still further the factor of safety.

Heretofore it has been customarmin building compact X-ray units, to employ a high tension transformer housed Withina cabinet and located at a little distance from the X-ray tube, the connection from the transformer to the X-ray tube being made by one or two high tension conductors.

Such apparatus offers many dangers, particularly to patients and the operator. By my invention I seek to prevent those dangers, or to reduce them to a minimum.

. It should be borne in mind that incidental to the use of a dental X-ray equipment the patient usually sits in a dental chair, which is connected with a water system and is thereby well grounded. Again, in using such an equipment, the operator may hold in his hand an electric switch or the like, which brings him into close contact with either a grounded part of the apparatus or the wir- .ing which supplies the low voltage currents. If, now, either the patient or the operator should happen to come too near certain parts of the high tension system, a discharge would take place,

causing a shock to the operator or to the patient,

as the case may be. A shock brought about in this manner is dangerous, and in some instances may cause death.

In the systems heretofore employed the high tension connections between the X-ray tube and the high tension transformer are subject to losses or" electrical energy, especially if the atmosphere is damp. These losses are known as corona losses, and they are very objectionable.

It has also been customary heretofore to place the X-ray tube and the high tension transformer for energizing the same into an oil tank so as to submerge the X-ray tube. While this avoids the dangers of exposed high tension connections extending between the X-ray tube and the transformer, it gives rise to troubles of other kinds.

By having the X-ray tube submerged in oil, carbonization is likely to take place upon the glass wall of the X-ray tube, and this process is made worse by the heat given oil from the cathode of the X-ray tube, this cathode being ordinarily heated to incandescence. And further, the oil being heated in this manner creates a necessity for compensating for the expansion of the oil, and increases the difficulty of maintaining the tank oil tight.

My invention is for the purpose of reducing the troubles above pointed out and so far as practicable doing away with them entirely.

The subject matter of this application is in the nature of a further development of the invention described in my patent of March 20, 1928, No.

Reference is made to the accompanying drawings forming a part of this specification and in which life reference characters indicate like parts throughout all of the figures.

Figure l is a substantially central vertical cross section, through one form of my device, here shown as a dental unit.

Figure 2 is a section on the line 22 of Figure 1, looking in the direction indicated by the arrows.

Figure 3 is a substantially vertical cross section through another form of my invention, adapted as an Y-ray unit for general use.

Figure 4 is a section on the line 44 of Figure 3, looking in the direction indicated by the arrows.

Figure 5 is a section on the line 55 of Figure 3, looking in the direction indicated by the arrows.

Figure 6 is a wiring diagram which is substantially adapted for either form of my device, but as shown is in connection with the form appear- 100 ing in Figures 1 and 2.

The X-ray unit shown in Figures 1 and 2 is suspended by means of trunnions 6, 6 extending through bearings '7, 7, these bearings being formed in the ends of a bow frame 8 carried by a stem 9, the latter being here shown as broken away.

The unit is housed within a container partially formed by a casing portion 10 of metal which. is suitably grounded and which has the form of a flat jar. A volume of cooling and insulating material 11, such as oil or jelly-like insulating material is contained within the casing portion 10 of the container. An outwardly extending flange 12 is provided on the casing portion 10 and is integral therewith.

A casing head 13 made of metal is carried by the casing portion 10 of the container or tank compartment, and normally closes the open end thereof to form a wall portion of the container. A gasket 14 is between the flange 12 and the adjacent portions of the casing head. Screws 15, 15 extend through the casing head and through the gasket and the flange 12, thus holding the casing head permanently in position and rendering it oil tight relatively to the casing.

A pair of supporting shelves 16 and 17 are,

carried by the casing head 13, and extend therefrom almost to the opposite end of the casing. These supporting shelves are provided respectively with braces 20, 21 integral with-themthe shelves and braces all being made of insulating material.

The supporting shelves 16 and 17 are also pro- 'vided' with anchor ends 18 and 19 integral therewith; these anchor ends being secured firmly to the casing head by means of screws 22.

" Parallel with the supporting shelves 16 and 17 are a pair of spacing shelves 23, 24, made of in- 'sulating material and provided with braces and 26 and anchor ends 27, 27. By means of screws 23, 23 the anchor ends 27 are secured firmly to" lugs 29, 29 with which the casing 10 is provided. By this arrangement the spacing shelves 23, 24 are held' firmly in position, opposite the supporting shelves 16 and 17. v 7 A high tension transformer core is shown at 30, and carries a high tension secondarywinding 31. At 32 is a very small low tension secondary winding, used to generate current for heating the cathode filament. This winding 32 may consist of a few turns of the high tension secondary winding 31, but in which the wire is thicker thanin the other turns of the secondary winding. v I

Another high tension winding is shown at 33, and contains a larger number of turns than the winding 31. r The winding 33develops about twothirds of the total voltage developed in' the transformer. Y

The casing head 13 of the container is provided with a neck 34,'integral with it and threaded internally.

' Extending from-this neck 34 is a tube holder of insulating material 35, having the form of a cylinder, thus forming a reentrant wall portion of the casing head 13 and of the container or tank compartment which is formed by the latter together with the casing 10.

The tube holder 35 is provided with a portion 36 of reduced diameter, threaded externally; and fitted upon this portion is a locking ring 37, made of metal and threaded internally. Between the locking ring 37 and the adjacent portion of the neck 34 is a gasket 38.

The tube holder 35 is provided with an annular shoulder 39, which fits neatly against the adjacent edge portion of the neck 34.

By this construction the tube holder 35 is fitted oil tight into the casing head 13 which forms a wall of the container.

The cylinder 35 is provided with an end portion 40 threaded internally, and fitting into this portion is a metallic closure cap 41, threaded externally. This closure cap 41 thus closes the open end of the cylinder 35 which together with the reentrant wall portion formed by the cylinder 35, the casing head 13, and casing 10, constitutes the walls of the entire container or tank compartment.

A gasket 42 engages the metallic closure cap 41, and is held in position by a locking ring 43. This locking ring is threaded externally, the adjacent inner portion of the cylinder 35 being threaded internallyv to receive it.

The metallic closure cap 41 carries a supporting sleeve 44 which has the general form of a pocket, as may be understood from Figure 1, and

is provided withradiator ribs 4411 which are immersed in the cooling and insulating material 11.

The entire metallic closure cap thus forms a heat dissipating means or radiator for the X-ray tube, as hereinafter more fully explained, as well as a wall of the container.

' An-X-ray tube is shown at 45, and is provided with a cathode stem 46 and an anode stem 47, the tube as a whole being substantially L-shaped, and being mounted exteriorly of its container or tank compartment. V

Tne X-ray tube is provided with a heat controlled cathode 43, here shown as in the form of a filament, and is further providedwith an anode 49, of the usual or any desired construction. The anode 49 is provided with a supporting stem 50, the latter having an end portion 51 which'fits neatly into the'supporting sleeve 44,

and engages a metallic washer 52, of substantially U-shape. A screw 53 extends through the end of the supporting sleeve 44 and into the end portion 51 ofthe' supporting stem. The screw 53 doestwo things; namely, it holds the supporting stem firmly in position and it serves as a bindingpostyf The casing head 13 is provided with a thickened portion 54 of'annular form. Extending'through this thickened portion is a tubular insulator 55, held inlposition by aid of a nut 56 and gasket 57, the insulator being thusrendered oil tight...

The'insulator '55 carries a collar 58, and supported within this collar is a socket 59 carrying a capIGO and enclosing the adjacent end portion of the cathode stem 46.

. The cathode 48 is heated by low tension currents supplied through wires 61 and 62, as hereinafter' more fully described.

The casing head 13 constituting a wall portion of the container is provided with a flange 63, and mounted uponthis flange is a casing cap 64, made of material which is as far as practicable opaque to X-rays. For this purpose I may use jglass, porcelain or other vitreous material,

permeated with salts of a dense metal, such as lead; or, instead, metallic lead or other dense metal or metals may be used. This casing cap surrounds the X-ray tube and is spaced substan tially equidistant therefrom to equalize the electrical field about the tube. .In order to fit the casing cap 64 in position it is provided with a flange 65, which fits neatly over the casing flange 63 and is detachably held in position by screws 66. The casing cap 64 is provided with a nozzle 67 and with a window 68, which is made rather thin, andof aluminum or other metal relatively transparent to X-rays. The window 68 may be made of material having suitable filtering properties to increase the skin tolerance of the patient, and as a precaution against over-dose.

The X-rays pass freely out through the window thus formed, and are as far as possible prevented from passing outwardly except through this window.

' The primary windings associated with the secondary windings 31 and 33 are not shown in Figures 1 and 2, but are indicated at 69 and 70 in the diagram, Figure 6.

It will be noted that the device as a whole is provided with two distinct compartments, namely, a compartment filled with oil or its equivalent in which all high tension parts except the X-ray tube are completely submerged, which is formed by the container comprising the casing 10, casing head 13, re-entrant cylinder 35,

and closure cap or heat dissipating means 41 anda compartment filled with air at atmospheric pressure and containing the X-ray tube which is formed by the closure can 64 secured to one of the walls, namely, the casing head 13.

It will also be noted that by simply removing the casing cap 64 the X-ray tube is rendered accessible to the operator, forpurposes of inspection, removal and repair.

The container and parts carried thereby constitute a complete and self-contained X-ray unit, carried by a support which is practically a swivel or universal joint.

In order to energize the unit, I prefer to employ an auto-transformer '71 connected with ordinary commercial low tension alternating current leads '72, '73 and energized thereby. A hand switch 72a is provided for throwing the auto-transformer into and out of action, and is thus used as an exposure switch.

The auto-transformer is provided with two switches 74, 75, for apportioning the output currents. A wire '76 leads from the switch 74 to the primary winding 69, and similarly a wire 77 leads from the switch '75 to the primary winding '70.

' Both the windings 69 and 70 are connected with the wire '78, which is a common return wire for the switches '74 and 75.

The wires '76 and '77 are flexible, and are led in through the wall of the casing 10 by means of scaled insulator connections, not here shown,'but well known in the art.

A wire '79 is connected with the'end portion 51 of the anode supporting stem 50, and extends therefrom to the secondary winding 33. A wire 80 is connected with the secondary winding 31, and. extends therefrom to a milliammeter 81. From the latter a wire 82 leads to secondary winding 33. A ground wire 83 is connected with the wire 82.

With the X-ray tube in operation the cathode 48, being heated to incandescence, of course throws ofi heat. But this heat does not reach the oil 11 or parts submerged therein, at least to any appreciable extent.

On the other hand the heat necessarily received by the anode 49 is transmitted along the stem 50 to the supporting sleeve 44, which is in direct contact with the oil 11. The ribs 44a of the supporting sleeve tend to diffuse this heat freely out into the body or" oil 11. The amount of heat being quite small, it does not unduly raise the temperature of the body of oil 11; and yet this operation prevents the anode 49 from becoming heated to a point where its efliciency would be impaired.

The auto-transformer switch 74 controls the primary winding 69 but has no effect upon the winding 70. Hence, the high tension secondary winding 31 and the low tension secondary winding'32 are together controllable by the switch 74. By this arrangement, therefore, the heating currents generated in the low tension winding 32 are proportionate to the high tension voltage generated in the secondary winding 31. The result is, that the heating currents and the secondary voltage are so controlled as to prevent the wellknown rise in the voltage which would ordinarily take place whenever the load upon the X-ray tube is decreased, or, conversely, when the current through the X-ray tube is increased. This increase, especially if the transformer is operating a. about its maximum load, is ordinarily accompanied by a substantial loss in secondary voltage. The switch "4 varies the current through the X-ray tube without causing the usual invers variation in the secondary voltage.

On the other hand the switch '75 changes the secondary voltage as generated by the secondary winding 33, in proportion to the variation applied to the primary winding '76, so that the milliamperage or current through the X-ray tube is controlled proportionately by means of the switch '75.

The hand switch 72a, which controls the auto transformer as a whole, is used for determining the time period of X-ray exposure. The switches 74 and '75 are set beforehand so as to apportion the voltage to be used for the exposure. The primary windings 69 and '70 are always energized simultaneously.

Thus it will be seen that instead of a single primary winding I use two primary windings mounted upon and energized by the same core, and controllable independently of each other.

I will next explain the form of my apparatus appearing in Figures 3, 4 and 5.

A contain r is partially formed by a casing body 84 which is made of metal and provided with a side wall 85 of the same material, these parts being fitted together edge to edge and united by a seam 86, which may be welded or soldered as shown at 87, in Figure 4.

The casing thus formed is an elongated hollow body provided at its ends with lobes 88 and 89, as indicat d more particularly in Figure 3.

The end portion of the casing, adjacent the lobe 88, is provided with an opening 96 of large size.

A closure plate 91, made of insulating material and forming a wall portion of the container, is fitted over this opening 90 in order to render the same oil tight, as may be understood from Figure 3. The closure plate 91 is provided with a brow 92, integral with it, and adapted to serve as a housing for one end of the X-ray tube, as hereinafter more fully described.

The casing 84 is further provided, adjacent the lobe 89, with an opening 93 of substantially circular form. A closure plate having a sub- 'stantially annular form, is so formed and fitted as to close the opening 93 and thus form a wall of the container.

The closure plate 94 carries a barrel 9 5 integral with it and having the form of a short cylinder which forms a reentrant wall portion in the container wall formed by the closure plate 94.

Detachably fitted into one end of barrel 95 and supported thereby is a closure cap 96. The clo sure cap is made of metal, and carries a supporting sleeve 97, also of metal and integral with it. This supporting sleeve has the form of a pocket, and carries a number of radiator ribs 97a which serve to distribute heat.

The closure cap 96, supporting sleeve 97, ribs 97a, thus form heat dissipating means or radiator as well as a wall portion of the con tainer in the same manner as previously described relative to the heat dissipating radiator 41 of Fig. 1. The entire container in this modification is :150

accordingly formed by the casing body 84, side wall 85, closure plates 91 and 94, re-entrant wall portion or barrel 95, and heat dissipating radiator or closure cap 96.

An X-ray tube is shown at 98, and is provided with a cathode stem 99 and with an anode stem 100. The X-ray tube is provided with a cathode 101 adapted to be heated, and here shown as having the form of a filament. This cathode is carried by a pair of wires 102, 103, through which it is energized.

Housed within the brow S2 and connected with the cathode stem 99 is a cathode coupling 104. Connected with this cathode coupling are a pair of wires 105, 166, used for supplying currents to the cathode filament 101 and also for energizing the X-ray tube.

The anode of the X-ray tube is shown at 107, and is carried upon a supporting stein 108, this supporting stem having an end portion 109, which extends into the supporting sleeve 97, above described.

The supporting sleeve 97 is also provided with a high tension connector 110, which serves practically as a binding post at this end of the Xray tube.

A casing cap is shown at 111 and is mounted upon the casing for the purpose of closing the compartment containing the X-ray tube.

The casing cap is provided with a window 112 which may be made of bakelite or of any other suitable material transparent to X-rays. This window may consist of a material having suitable filtering properties to protect the skin of the patient and to prevent the dangers of over dosage.

Bounding this window 112 is a conoidal memher 113 made of insulating material, and used as in other machines well known in this art.

The casing cap 111 is held in position by means of screws 114. By removing these screws the casing cap can be taken oif.

The enclosure within the casing cap 111 i simply a compartment which is filled with air at atmospheric pressure.

A supporting bracket 115 made of insulating material is by means of screws 116 detachably mounted upon the supporting plate 91. Another supporting bracket of insulating material is shown at 117, and is mounted upon the inner surface of the lobe 89, and detachably held in position by screws 118.

A transformer core is shown at 119, and extends lengthwise through the casing. Encircling this transformer core are high tension windings 120 and 122, and also a low tension winding 121, the latter being made of a few turns from the winding 126. The low tension winding 121 is for the purpose of generating currents to heat the cathode 101; or in other words, has a function like that of the winding 32, above described with reference to Figures 1 and 2.

A terminal connection is shown at 123, and to the latter is connected a ground wire 124.

From the terminal connection 123 a wire 125 leads to the milliammeter 81, and from the latter a wire 126 leads through an insulating seal 127 to the secondary winding 122.

A volume of insulating and cooling material 128, preferably oil, fills the casing and envelopes the high tension transformer.

Except as above described the structure and action of the mechanism shown in Figures 3, 4 and 6 is like that above described with reference to the other figures.

The wiring for mechanism shown in Figures 3, 4 and 5 is substantially like, that shown in the diagram Figure 6, and the two large secondary windings are controlled separately by means of the hand switches 74 and. 75, substantially as above described in detail.

My two forms of apparatus are very much alike as regards both structure and operation.

In each of these, all high tension parts except the X-ray tube are housed within a single compartment, and submerged in insulating oil or its equivalent. In each of the two forms the X-ray tube alone is in a separate compartment from the other high tension parts, and is in air, at atmospheric pressure.

In each of the two forms the operator, by re- 2;,

moving the casingcap, has access to the X-ray tube and its mountings. 7

No carbonization can take place in the insulating oil, and no carbonization of the insulating oil can subject the X-ray tube to incrustation or other deleterious efiects due to carbonization.

In the construction and operation of each form of my device, the factor of safety is the most important consideration. If the apparatus be made in a workmansln'p manner and used under average conditions of operation, there is no danger of shock to the patient or to the operator, and no danger of accident to the apparatus. Such being the case the apparatus is also foolproof, as this term isaccepted in the art.

I do not limit myself to the precise mechanism shown, as variations may be made therein without departing from my invention the scope of which is commensurate with my, claims.

Having thus described myinvention, what I claim as new and desire to secure by Letters Patent is as follows:- v

1, In a safety X-ray unit thecombination of a container, a volume of oil contained in said container and used for insulating and cooling, a high tension transformer mounted in said container and submerged in said volume of oil, said transformer being .providedwith a low-tension secondary winding for generatingheating currents and a high-tension secondary winding for supplying high potential energy, heat dissipating means forming a part of said container and in contact with said volume of oil, an X-ray tube 1 supported by said container exteriorly thereof and provided witha cathode to be heated, said X-ray tube being further provided with an anode which is heated during operation of said tube, said anode being in heat conducting communication with said heat dissipating means for transhigh tension transformer provided with a single 11 core and with two primary windings and a plurality of secondary windings mounted upon said core, said transformer comprising a unitary structure arranged within said container, a volume of insulating and cooling material disposed in said container andsubmerging said transformer, heat dissipating means forming a part of said container and communicating with the interior thereof inclosing said transformer and said insulating and cooling material, an X-ray tube positioned exteriorly of said container and having a portion thereof in heat conducting communication with said heat dissipating means, said secondary windings being electrically connected to said X-ray tube for energizing the same, and mechanism loll connected with said primary windings for controlling said primary windings independently of each other as effecting said secondary windings.

3. An X-ray apparatus comprising a tube of insulating material, a closure means carried by said tube of insulating material and capable of absorbing heat from the anode of an X-ray tube, an X-ray tube provided with cathode and anode terminals and supported by said closure means, a transformer located adjacent said insulator tube, a casing containing an insulating and cooling medium surrounding said transformer and said insulator tube, a cover plate on said casing supporting said insulator tube and a second insulator through said cover plate, said second mentioned insulator supporting the cathode terminal of said X-ray tube, and electrical connections from said transformer to the terminals of said X-ray tube.

4. In an X-ray apparatus the combination of an X-ray tube with a cathode and an anode to be cooled, said X-ray tube being housed in an air filled housing to prevent electrical discharges from the said X-ray tube to grounded objects outside said housing, a casing adjoining said air filled housing, an insulating and cooling medium in said casing, the anode of said X-ray tube being in heat conducting communication with the cooling and insulating mediurn in said casing, a transformer in said casing immersed in said cooling and insulating medium and connected to said X-ray tube for energizing said X-ray tube, said transformer provided with two independently controllable primaries, a coacting secondary for each and a third Wmding for heating the cathode of said X-ray tube.

ARTHUR MUTSCI-IELLER. 

